1. Field of the Invention
The present invention relates to a laminated electronic component and a mounting structure thereof.
2. Description of the Related Art
In recent years, as development of electronic equipment with higher performance advances rapidly, laminated ceramic capacitors have larger capacitances. In a large-capacitance laminated ceramic capacitor, a high dielectric ceramic such as barium titanate is used as a material constituting a dielectric.
Such a high dielectric ceramic has piezoelectric and electrostrictive properties. Thus, a laminated ceramic capacitor including a dielectric made of a high dielectric ceramic has a mechanical strain when a voltage or an electric field is applied thereto.
Therefore, when an alternating current (AC) voltage, or a direct current (DC) voltage having an AC component superimposed thereon is applied to the laminated ceramic capacitor, vibration due to the mechanical strain is generated. When the laminated ceramic capacitor is connected to a circuit substrate, the vibration is transmitted to the circuit substrate, causing the circuit substrate to vibrate.
When vibration of the air around the circuit substrate thus generated is within a range of 20 Hz to 20 kHz, which is the audible frequency range, it generates an unpleasant sound to human ear. This sound-generating phenomenon is called “acoustic noise”.
Conventionally, some proposals have been made to prevent and suppress such acoustic noise. One exemplary technique for reducing acoustic noise is described in Japanese Patent Laying-Open No. 2000-232030.
In a method for mounting laminated ceramic capacitors on a circuit substrate described in Japanese Patent Laying-Open No. 2000-232030, lands for mounting the capacitors which are conductive to each other are formed on both front and back surfaces of the circuit substrate at substantially plane-symmetrical positions, and the laminated ceramic capacitors are arranged on these lands, respectively, for conductive connection. In this technique, it is expected that vibration transmitted from one laminated ceramic capacitor to the circuit substrate and vibration transmitted from the other laminated ceramic capacitor to the circuit substrate cancel each other out and suppress generation of acoustic noise.
According to the invention described in Japanese Patent Laying-Open No. 2000-232030, it is necessary to mount two laminated ceramic capacitors having an equal specification on both of the front and back surfaces of the circuit substrate, and thus the degree of freedom in designing the circuit substrate is lost.